The object of these investigations is to elucidate the biochemical mechanisms responsible for the reduced cardiac function and mortality that may follow open heart surgery. The availability of sufficiently refined methods of studying the cellular chemistry of relatively intact human myocardium obtained by drill biopsy at the time of cardiac surgery has made such a study possible. Histochemical and biophysical studies will be performed on biopsy specimens removed at different stages of an operation. More importantly, such an approach will allow biochemical procedures to be applied to myocardial samples in which the spacial relationships of the various sub-cellular components are retained. The results of these studies will be correlated with the duration of by-pass and the postoperative course of the patient. Once the functional abnormalities are identified, it may be possible to begin to discover what is required to restore the function of such dysfunctional myocardium.